Cerebrospinal Fluid Physiology Research Articles

The Role of Phase-Contrast MRI in Diagnosing Cerebrospinal Fluid Flow Abnormalities.

Background Cerebrospinal fluid (CSF) dynamics play a crucial role in maintaining the homeostasis of the central nervous system (CNS). Any disruption in CSF flow can lead to various congenital and acquired conditions, impacting neurological function and overall health. This study aims to analyze the significance of phase-contrast MRI in evaluating abnormalities in CSF flow and its diagnostic utility in various CSF-related disorders. Phase contrast MRIhas emerged as a valuable tool for evaluating CSF dynamics non-invasively by examining CSF flow characteristics such as pulsatile flow patterns, hyperdynamic or hypodynamic flow, and disruptions in CSF circulation. Alterations in CSF pulsatility and stroke volume can indicate changes in intracranial compliance, vascular resistance, or CSF production and absorption rates. The findings of this study will advance our understanding of CSF physiology and its relevance in neurological pathologies, potentially leading to improved patient outcomes and management approaches. Materials and methods The study involved 36 patients and was conducted as an observational, prospective study over 18 months (October 2020 to March 2022) at the Department of Radiology, Saveetha Medical College and Hospital, Chennai. We utilized a 1.5 T Philips Multiva MRI scanner by Philips Healthcare in Amsterdam, Netherlands.The study included patients with suspected CSF flow abnormalities and abnormal MRI findings (normal pressure hydrocephalus (NPH), age-related brain atrophy, aqueduct stenosis (AS), Chiari malformation type 1, syringomyelia, or arachnoid cyst), alongside control exhibiting normal neurological symptoms and MRI results. Exclusions involved individuals with febrile seizures, neurological diseases, cerebrovascular accidents, anti-convulsive medication use, cardiac arrhythmia, or MRI contraindications. Post-processing involved analyzing stroke volume (SV), peak systolic velocity (PSV), end diastolic velocity (EDV), and mean flux. Statistical analysis was conducted using the StatisticalPackage for the Social Sciences (IBMSPSSStatisticsforWindows,IBMCorp., Version 24.0, Armonk,NY), employing the χ2-test for categorical variables and nonparametric tests like Mann-Whitney U and Kruskal-Wallis H-tests for quantitative variables. A p-value < 0.05 was considered significant. Results The 36 patients, aged 1 to 80 years, were referred by the neurology department and categorized into four subgroups based on clinical history and conventional MRI findings: NPH, AS, age-related brain atrophy, and a normal control group. MRI CSF flowmetry evaluation focused on PSV, PDV, and SV. We found peak diastolic velocity (PDV), PSV, and average blood velocity (ABV) to be significantly higher in NPH compared to the control group (PSV, EDV, and SV: 9.96 +/- 1.73, 4.72 +/- 0.62, and 63 +/- 12.88 for NPH versus 4.8 +/- 0.39, 3.21 +/- 0.55, and 20.72 +/- 5.7 for control, respectively; p = 0.000). Conversely, patients with age-related brain atrophy and AS exhibited lower values (1.6 +/- 0.44, 1.13 +/- 0.09, and 6.33 +/- 2.08 for AS, and 2.07 +/- 0.09, 1.62 +/- 0.33, and 6.8 +/- 2.16 for age-related brain atrophy versus control; p = 0.002). Conclusion MRI CSF flowmetry emerges as a rapid, accurate, and non-invasive diagnostic tool for various neurological disorders associated with abnormal CSF flow. Additionally, this technique may aid in selecting appropriate treatment strategies.

Endoscopic third ventriculostomy versus ventriculoperitoneal shunt in patients of hydrocephalus in eastern India: A prospective observational study

Background: Hydrocephalus is a disorder of cerebrospinal fluid (CSF) physiology, resulting in an abnormal enlargement of the ventricles due to excessive accumulation of CSF. Although neurosurgical treatment has evolved over time with ventriculoperitoneal shunt (VPS) as the standard of care, procedure-related complications and poor long-term cognitive and motor milestone outcomes are still considerable, justifying the need for safer alternatives. Endoscopic third ventriculostomy (ETV) has emerged as a promising prospect especially in non-communicating hydrocephalus (NCH). Aims and Objectives: To compare the beneficial effects of ETV versus ventriculoperitoneal shunt in patients of NCH. Materials and Methods: The present prospective study was conducted at the Department of Neurosurgery, Bangur Institute of Neurosciences, IPGMER and SSKM Hospital, Kolkata from July 2021 to December 2022 among 60 patients admitted with NCH. Out of 60 patients; 30 patients underwent ETV and the remaining 30 patients VP shunting. All included patients had their history taken and relevant clinical and radiological examination done pre-operatively. They were discharged on the third post-operative day or later depending on their clinical condition and recovery. Results: Aqueductal stenosis was the most common etiology for NCH in both the groups. Post-intervention, complications and reoperation rate were reported more in VP group as compared to ETV group. Overall 3 subjects died, out of which 2 belonged to VP group and 1 to ETV group. Success was found in 70% and 86.67% of the subjects in VP and ETV group respectively. Conclusion: In patients with non-communicating or obstructive hydrocephalus, ETV was reported to be superior to VPS in terms of reoperation and complication rate at 4th, 12th, and 24th weeks after the treatment.

Severe hyperglycorrhachia and status epilepticus after endoscopic aqueductoplasty: illustrative case.

While hypoglycorrhachia is observed and managed frequently, there are few reports in the literature of clinically significant hyperglycorrhachia after neurosurgery. Understanding the effects and management of severe hyperglycorrhachia is important to the neurosurgeon and neurocritical care teams who care for patients in these rare scenarios. The authors present the case of a 3-month-old male with congenital hydrocephalus who faced profound hyperglycorrhachia and status epilepticus after an endoscopic aqueductoplasty using an irrigant composed of lactated Ringer's solution with dextrose 5% in water. A multidisciplinary approach was developed to monitor and treat the patient's seizures and cerebrospinal fluid (CSF) osmolytes. This case provides several learning opportunities for understanding CSF physiology, pathogenesis of common brain injuries related to osmotic shifts and inflammatory states, as well as clinical management of hyperglycorrhachia. It also reiterates the significance of meticulous intraoperative assessment to avoid preventable medical errors.

346 Development of Deuterium Magnetic Resonance Imaging for Cerebrospinal Fluid Studies

INTRODUCTION: Over the past ten years, the role of the glymphatic system has been defined and explored using various cerebrospinal fluid (CSF) tracers to track the movement of CSF through the perivascular spaces and into the brain interstitium. Glymphatic studies most commonly use gadolinium as a CSF tracer, which is not blood-brain-barrier (BBB) soluble. The primary component of CSF is water, however, which is BBB permeable. Cerebrospinal fluid may behave differently than large molecule tracers. Heavy water (D2O) is an isotope of water often used in physiology studies. We hypothesized that D2O would provide a traceable MR signal in the brain, allowing for more physiologically realistic models of CSF flow within the glymphatic system. METHODS: Two adult male rats underwent deuterium enhanced MR imaging. Images were obtained using a custom-made RF transmit/receive coil from Rapid MR International that is dual tuned to both proton (1H, 300.3 MHz) and deuterium (2H, 46.1 MHz) resonant frequencies for use in a 7 Tesla Bruker MRI system. After appropriate system calibration for optimization of deuterium MR signal with intravenous D2O infusion, the rats underwent spinal catheter implantation for intrathecal infusion. Images were taken during and after D2O infusion to evaluate uptake and clearance. RESULTS: Deuterium produced a imageable MR signal in the brain with intravenous and intrathecal infusion. Complete signal washout was noted within 10 minutes of stopping the intrathecal infusion. CONCLUSIONS: Deuterium MRI holds promise as a physiologic CSF tracer. As the technique is refined, it can be used for further CSF physiology studies. The rapid clearance of intrathecal D2O as compared to previous models using gadolinium supports our theory that CSF behaves differently than the large molecule tracers historically used to characterize its flow.

Review of Cerebrospinal Fluid Physiology and Dynamics: A Call for Medical Education Reform

The flow of cerebrospinal fluid (CSF) has been described as a unidirectional system with the choroid plexus serving as the primary secretor of CSF and the arachnoid granulations as primary reabsorption site. This theory of neurosurgical forefathers has been universally adopted and taught as dogma. Many neuroscientists have found difficulty reconciling this theory with common pathologies, and recent studies have found that this "classic" hypothesis may not represent the full picture. To review modern CSF dynamic theories and to call for medical education reform. We reviewed the literature from January 1990 to December 2020. We searched the PubMed database using key terms "cerebrospinal fluid circulation," "cerebrospinal fluid dynamics," "cerebrospinal fluid physiology," "glymphatic system," and "glymphatic pathway." We selected articles with a primary aim to discuss either CSF dynamics and/or the glymphatic system. The Bulat-Klarica-Orešković hypothesis purports that CSF is secreted and reabsorbed throughout the craniospinal axis. CSF demonstrates similar physiology to that of water elsewhere in the body. CSF "circulates" throughout the subarachnoid space in a pulsatile to-and-fro fashion. Osmolarity plays a critical role in CSF dynamics. Aquaporin-4 and the glymphatic system contribute to CSF volume and flow by establishing osmolarity gradients and facilitating CSF movement. Multiple studies demonstrate that the choroid plexus does not play any significant role in CSF circulation. We have highlighted major studies to illustrate modern principles of CSF dynamics. Despite these, the medical education system has been slow to reform curricula and update learning resources.

The Sheep as a Comprehensive Animal Model to Investigate Interdependent Physiological Pressure Propagation and Multiparameter Influence on Cerebrospinal Fluid Dynamics.

The present study aims to develop a suitable animal model for evaluating the physiological interactions between cerebrospinal fluid (CSF) dynamics, hemodynamics, and abdominal compartment pressures. We seek to contribute to the enhanced recognition of the pathophysiology of CSF-dependent neurological disorders like hydrocephalus and the improvement of available treatment options. To date, no comprehensive animal model of CSF dynamics exists, and establishing an accurate model will advance our understanding of complex CSF physiology. Persisting knowledge gaps surrounding the communication and pressure propagation between the cerebrospinal space and adjacent anatomical compartments exacerbate the development of novel therapies for neurological diseases. Hence, the need for further investigation of the interactions of vascular, craniospinal, and abdominal pressures remains beyond dispute. Moreover, the results of this animal study support the optimization of in vitro test benches for medical device development, e.g., ventriculoperitoneal shunts. Six female white alpine sheep were surgically equipped with pressure sensors to investigate the physiological values of intracranial, intrathecal, arterial, central venous, jugular venous, vesical pressure, and four differently located abdominal pressures. These values were measured simultaneously during the acute animal trial with sheep under general anesthesia. Both carotid and femoral arterial blood pressure indicate a reliable and comparable representation of the systematic blood pressure. However, the jugular venous pressure and the central venous pressure in sheep in dorsal recumbency do not correlate well under general anesthesia. Furthermore, there is a trend for possible comparability of lateral intraventricular and lumbar intrathecal pressure. Nevertheless, animal body position during measurements must be considered since different body constitutions can alter the horizontal line between the cerebral ventricles and the lumbar subarachnoid space. While intra-abdominal pressure measurement in the four different abdominal quadrants yielded greater inter-individual variability, intra-vesical pressure measurements in our setting delivered comparable values for all sheep. We established a novel and comprehensive ovine animal model to investigate interdependent physiologic pressure propagation and multiparameter influences on CSF dynamics. The results of this study will contribute to further in vitro bench testing, the derivation of novel quantitative models, and the development of a pathologic ovine hydrocephalus model.

Investigation of the Presence of Arachnoid Granulation in Fetuses and Early Infancy

AbstractThe aim of our study is to investigate the importance of arachnoid granulation in cerebrospinal fluid physiology in fetuses and early infancy. Using the random sampling method, postmortem fetuses more than 26 weeks of gestation age and the children under the age of 1 year were chosen from the autopsy materials. Two male and two female intrauterine dead fetus; three male and three female, totally six children under the age of 1 year and one 3-year-old male were included in this study. In cases of intrauterine fetuses more than 26 weeks of gestation and children under the age of 1 year, complete invagination of arachnoid villi into the superior sagittal sinus was examined histologically. In the intrauterine period and in the first 6 months of life, arachnoid villi structures were not found in histologic preparations although in preparations taken after the 6 months of life samples showed similarities to arachnoid granulations. These structures were considered as arachnoid villi drafts after immunohistochemical analysis. In the control case who were 3 years old, maturation of arachnoid villi was complete and the arachnoid villi were invaginated into the superior sagittal sinus as fingerlike extensions. In our study, we think that the failure after E3V intervention in the treatment of hydrocephalus in cases under the age of 1 years may be related to the completion of arachnoid granulation development after the 18th month of life and the immature resorption capacity in this period.

Abstracts from Hydrocephalus 2021: The Thirteenth Meeting of the International Society for Hydrocephalus and Cerebrospinal Fluid Disorders

Abstracts from Hydrocephalus 2021: The Thirteenth Meeting of the International Society for Hydrocephalus and Cerebrospinal Fluid Disorders

The physiology and pathophysiology of cerebrospinal fluid: new evidence

The physiology and pathophysiology of cerebrospinal fluid: new evidence

The role of mesencephalic aqueduct obstruction in hydrocephalus development: a case report

We report on three patients with mesencephalic aqueduct obstruction, which completely blocked the cerebrospinal fluid communication between the third and fourth cerebral ventricle, demonstrated by standard and high-resolution magnetic resonance sequences. Only one patient developed radiological and clinical presentation of hydrocephalus, without radiological signs of increased intraventricular pressure. The remaining two patients did not show clinical signs of hydrocephalus and had a normal radiological presentation of the ventricular system. These findings contradict the classical concept of cerebrospinal fluid physiology. This concept assumes a unidirectional circulation of cerebrospinal fluid through the mesencephalic aqueduct from the secretion site, predominantly in the choroid plexuses, to the resorption site, predominantly in the dural venous sinuses. Therefore, the obstruction of the mesencephalic aqueduct would inevitably lead to triventricular hypertensive hydrocephalus in all patients. The current observations, however, accord with the new concept of cerebrospinal fluid physiology, which postulates that cerebrospinal fluid does not circulate unidirectionally because it is both formed and resorbed along the entire capillary network within the central nervous system.

Elevated Mitochondrial Reactive Oxygen Species within Cerebrospinal Fluid as New Index in the Early Detection of Lumbar Spinal Stenosis.

Lumbar spinal stenosis (LSS) is a common neurodegenerative condition. However, how neurogenic claudication develops with severe leg pain has not yet been clearly elucidated. Moreover, cerebrospinal fluid (CSF) physiology at the lumbosacral level is poorly understood because of the difficulties involved in quantification and visualization. Recent studies have suggested that assessment of mitochondrial function in CSF provides an indirect way to assess neurological disorders and an important feature of disease progression. In this study, we assessed the relevance of endogenous extracellular mitochondria in the CSF of rats after LSS. Mitochondrial changes within the CSF were analyzed following LSS at 1 week using flow cytometry. An increase in cell size and number was observed in CSF with LSS, and reactive oxygen species (ROS) levels were also increased within the CSF at 1 week in the LSS group. Elevated mitochondrial ROS and functional changes in the CSF are hallmarks of LSS. The present study is the first to demonstrate that elevated mitochondrial ROS within the CSF is a new index for the early detection of LSS. Moreover, it may represent a potential novel treatment target for LSS.

The Need for Head Space: Brachycephaly and Cerebrospinal Fluid Disorders.

Brachycephalic dogs remain popular, despite the knowledge that this head conformation is associated with health problems, including airway compromise, ocular disorders, neurological disease, and other co-morbidities. There is increasing evidence that brachycephaly disrupts cerebrospinal fluid movement and absorption, predisposing ventriculomegaly, hydrocephalus, quadrigeminal cistern expansion, Chiari-like malformation, and syringomyelia. In this review, we focus on cerebrospinal fluid physiology and how this is impacted by brachycephaly, airorhynchy, and associated craniosynostosis.

Extensive Healthy Donor Age/Gender Adjustments and Propensity Score Matching Reveal Physiology of Multiple Sclerosis Through Immunophenotyping.

Quantifying cell subpopulations in biological fluids aids in diagnosis and understanding of the mechanisms of injury. Although much has been learned from cerebrospinal fluid (CSF) flow cytometry in neuroimmunological disorders, such as multiple sclerosis (MS), previous studies did not contain enough healthy donors (HD) to derive age- and gender-related normative data and sufficient heterogeneity of other inflammatory neurological disease (OIND) controls to identify MS specific changes.The goals of this blinded training and validation study of MS patients and embedded controls, representing 1,240 prospectively acquired paired CSF/blood samples from 588 subjects was (1) to define physiological age-/gender-related changes in CSF cells, (2) to define/validate cellular abnormalities in blood and CSF of untreated MS through disease duration (DD) and determine which are MS-specific, and (3) to compare effect(s) of low-efficacy (i.e., interferon-beta [IFN-beta] and glatiramer acetate [GA]) and high-efficacy drugs (i.e., natalizumab, daclizumab, and ocrelizumab) on MS-related cellular abnormalities using propensity score matching.Physiological gender differences are less pronounced in the CSF compared to blood, and age-related changes suggest decreased immunosurveillance of CNS by activated HLA-DR+T cells associated with natural aging. Results from patient samples support the concept of MS being immunologically single disease evolving in time. Initially, peripherally activated innate and adaptive immune cells migrate into CSF to form MS lesions. With progression, T cells (CD8+ > CD4+), NK cells, and myeloid dendritic cells are depleted from blood as they continue to accumulate, together with B cells, in the CSF and migrate to CNS tissue, forming compartmentalized inflammation. All MS drugs inhibit non-physiological accumulation of immune cells in the CSF. Although low-efficacy drugs tend to normalize it, high-efficacy drugs overshoot some aspects of CSF physiology, suggesting impairment of CNS immunosurveillance. Comparable inhibition of MS-related CSF abnormalities advocates changes within CNS parenchyma responsible for differences in drug efficacy on MS disability progression.Video summarizing all results may become useful educational tool.

The Regulation of Cerebral Spinal Fluid Flow and Its Relevance to the Glymphatic System.

The glymphatic system is a relatively new concept that has been associated with regulation of cerebrospinal fluid (CSF), as well as brain waste clearance. Novel techniques to study glymphatic dysfunction have in turn prompted a reassessment of brain physiology and underlying elements of neurological disease. This review incorporates a contemporary imaging perspective focused on understanding the regulation of CSF flow, thus expanding the putative clinical relevance of this system and the relationships between CSF flow and glymphatic function. MR imaging studies, especially those that employ intrathecal gadolinium contrast, have identified potentially new pathways regulating CSF production, absorption, and clearance. These studies, when viewed in the context of more historical anatomic descriptors of CSF production and absorption, provide a more robust description of CSF physiology and waste clearance. CSF production and resorption are under-investigated and could be related to various pathophysiologic processes in neurodegeneration. Anatomically based clinical exemplars of CSF clearance are discussed. Future studies should focus on linking glymphatic functionality with neurological disease.

Development of a straight vertebrate body axis.

The vertebrate body plan is characterized by the presence of a segmented spine along its main axis. Here, we examine the current understanding of how the axial tissues that are formed during embryonic development give rise to the adult spine and summarize recent advances in the field, largely focused on recent studies in zebrafish, with comparisons to amniotes where appropriate. We discuss recent work illuminating the genetics and biological mechanisms mediating extension and straightening of the body axis during development, and highlight open questions. We specifically focus on the processes of notochord development and cerebrospinal fluid physiology, and how defects in those processes may lead to scoliosis.

Cerebrospinal fluid dynamics with its surgical implications

Cerebrospinal fluid (CSF) is largely (70-80%) produced by the choroids plexus of the ventricles and is considered as the plasma ultrafiltrate. While CSF formation, circulation, and composition appear to be physiological and physical, its absorption appears to be mainly physical. The formation, composition, circulation, absorption, and changes in pathological conditions of CSF are discussed briefly in this review article. The CSF pressure dynamics studies provide information about the tightness, elastance, or outflow resistance of the CSF in the CNS. We believe that the present study shall help to provide essential details of CSF physiology which are important to many disciplines including radiology, neurology, and neurosurgery.

Idiopathic Intracranial Hypertension: Glymphedema of the Brain.

During the last decade, our understanding of cerebrospinal fluid (CSF) physiology has dramatically improved, thanks to the discoveries of both the glymphatic system and lymphatic vessels lining the dura mater in human brains. We detail the recent basic science findings in the field of CSF physiology and connect them with our current understanding of the pathophysiology of idiopathic intracranial hypertension (IIH). Transverse sinus (TS) stenoses seem to play a major causative role in the symptoms of IIH, as a result of a decrease in the pressure gradient between the venous system and the subarachnoid space. However, the intracranial pressure can be highly variable among different patients, depending on the efficiency of the lymphatic system to resorb the CSF and on the severity of TS stenoses. It is likely that there is a subclinical form of IIH and that IIH without papilledema is probably under-diagnosed among patients with chronic migraines or isolated tinnitus. IIH can be summarized in the following pathological triad: restriction of the venous CSF outflow pathway-overflow of the lymphatic CSF outflow pathway-congestion of the glymphatic system. To better encompass all the stages of IIH, it is likely that the Dandy criteria need to be updated and that perhaps renaming IIH should be considered.

The Reissner Fiber Is Highly Dynamic In Vivo and Controls Morphogenesis of the Spine

Cerebrospinal fluid (CSF) physiology is important for the development and homeostasis of the central nervous system, and its disruption has been linked to scoliosis in zebrafish [1, 2]. Suspended in the CSF is an extracellular structure called the Reissner fiber, which extends from the brain through the central canal of the spinal cord. Zebrafish scospondin-null mutants are unable to assemble a Reissner fiber and fail to form a straight body axis during embryonic development [3]. Here, we describe hypomorphic missense mutations of scospondin, which allow Reissner fiber assembly and extension of a straight axis. However, during larval development, these mutants display progressive Reissner fiber disassembly, which is concomitant with the emergence of axial curvatures and scoliosis in adult animals. Using a scospondin-GFP knockin zebrafish line, we demonstrate several dynamic properties of the Reissner fiber invivo, including embryonic fiber assembly, the continuous rostral to caudal movement of the fiber within the brain and central canal, and subcommissural organ (SCO)-spondin-GFP protein secretion from the floor plate to merge with the fiber. Finally, we show that disassembly of the Reissner fiber is also associated with the progression of axial curvatures in distinct scoliosis mutant zebrafish models. Together, these data demonstrate a critical role for the Reissner fiber for the maintenance of a straight body axis and spine morphogenesis in adult zebrafish. Our study establishes a framework for future investigations to address the cellular effectors responsible for Reissner-fiber-dependent regulation of axial morphology. VIDEO ABSTRACT.

The legacy of Malcolm Beverley Segal (1937\u20132019) on the science and fields concerned with choroid plexus and cerebrospinal fluid physiology

This article highlights the scientific achievements, professional career, and personal interactions of Malcolm B. Segal who passed away in July this year. Born in 1937 in Goodmayes, Essex, UK, Segal rose to the Chairman position in the Division of Physiology at United Medical and Dental School of Guy’s and St. Thomas’ Hospitals, retiring in 2006 after his long professional career in biomedical science. Being trained in Hugh Davson’s laboratory, Segal became one of the pioneers in research on cerebrospinal fluid physiology and the choroid plexus. During the course of his career, Segal himself trained a number of young scientists and collaborated with many colleagues around the world, making long-lasting friendships along the way. In addition to his professional accomplishments as a researcher and educator, Segal was an avid sailor and wine connoisseur, and enjoyed teaching classes on navigation and wine tasting.

The Reissner Fiber is Highly Dynamic in Vivo and Controls Morphogenesis of the Spine

Spine morphogenesis requires the integration of multiple musculoskeletal tissues with the nervous system. Cerebrospinal fluid (CSF) physiology is important for development and homeostasis of the central nervous system and its disruption has been linked to scoliosis in zebrafish. Suspended in the CSF is an enigmatic glycoprotein thread called the Reissner fiber, which is secreted from the subcomissural organ (SCO) in the brain and extends caudally through the central canal to where it terminates at the base of the spinal cord. In zebrafish, scospondin null mutants are unable to assemble the Reissner fiber and fail to extend a straight body axis during embryonic development. Here, we describe zebrafish hypomorphic missense alleles, which assemble the Reissner fiber and straighten the body axis during early embryonic development, yet progressively lose the fiber, concomitant with the emergence of body curvature, alterations in neuronal gene expression, and scoliosis in adults. Using an endogenously tagged scospondin-GFP zebrafish knock-in line, we directly visualized Reissner fiber dynamics during the normal development and during the progression of scoliosis, and demonstrate that the Reissner fiber is critical for the morphogenesis of the spine. Our study establishes a framework for future investigations of mechanistic roles of the Reissner fiber including its dynamic properties, molecular interactions, and how these processes are involved in the regulation of spine morphogenesis and scoliosis.